Process of manufacturing lithium acetylsalicylate.



ALBERT BUSCH, OF BRUNSWICK,

nnr ornrcii.

GERMANY, ASSIGNOR TO THE FIRM OF JOHANN A.

WUELFING, 0F BERLIN, GERMANY.

PROCESS OF MANUFACTURING LITHIUM ACETYLSALICYLATE.

No Drawing.

To all whom it may concern:

Be it known that I, ALBERT Boson, doctor of philosophy, chemist, a subject of the Duke of Brunswick, residing in Brunswick, in the Dukedom of Brunswick, Germany, have invented a new and useful Process of Manufacturing Lithium Acetylsalicylate, of which the following is a specification.

The manufacture of alkali salts of acetylsalicylic acid, which have certain advantages over the free acid, presents several difiiculties, owing to the ease with which this acid is decomposed. According to English Patent specification No. 15517 /1902 and German Patent specification No. 218467 or the corresponding English Patent specification No.

29439/1909, the general mode of producing these salts is to dissolve or suspend the acetylsalicylic acid in a suitable organic liquid and then add the equivalent proportion of alkali, in the first case caustic alkali in alcoholic solution, in the latter alkali carbonate. It is the object of these processes to obtain the alkali salts of the acetylsalicylic acid, which are formed, in solution in the added medium; the solution is then filtered or not, and the alkali salt separated from it by crystallization, or by adding a precipitant, such as ether. These processes have the serious disadvantage that in the first place they require a considerable quantity of a solvent and precipitant and secondly more or less of the acetylsalicvlic acid is de composed by the alkali according to the duration of action. For this reason the German Patent specification 218467 or the corresponding English Patent specification 29-139/ 1909 prescribe immediate filtration of the solution obtained, and its precipitation with ether for separating the alkali salt as quickly as possible. On these grounds, therefore, the said processes are not very practicable. They require two different liquids, a solvent and a precipitant, both in large proportions, and these liquids are only with diificulty to be separated for recovering them. Moreover a part of the acetylsalicylic acid is decomposed.

According to the present invention any alkali salt, but especially the lithium salt of the acetylsalicylic acid can be made with use of a single organic liquid whlch 1s requ red only in a comparatively small proportion, when used on certain conditions, to be described below, no crystallization being neces- Speeifleation of Letters Patent.

' theoretical that in the new process comparatively Patented Mar. 2, 1915.

Application filed February 25, 1914. Serial No. 820,886.

sary and theoutput coming up almost to the yield, as no loss and no decomposition of aeetylsalicylic acid will occur.

I have found out that an intimate and dry mixture of equivalent parts'by weight of acetylsalicylic acid and lithium carbonate can be easily converted into lithium acetylsalicylate by iuoistening the mixture with a small proportion of an alcohol or a ketone of the aliphatic series and kneading or stirring the mass, till ,a sample dissolves in water readily and without evolution of carbon dioxid. As alcohols methylalcohol and ethylalcohol, as ketones acetone and methylethyh ketone can be used for the purpose, either in an anhydrous state or containing small quantities of water. Instead of the pure organic liquids, mixtures in dillcrent proportions may be used as well for the purpose.

To obtain a quite neutral lithium salt of the acetylsalicylic'acid, the organic solvent' used for converting a mixture of equivalent parts by weight of acetylsalicylic acid and lithium carbonate into lithium acetylsalicylate has to act upon the mixture for a certain time. \Vhen the mixture is finished and worked up shortly after moistening it with the solvent used, the lithium salt will show an alkaline reaction owing to lithium carbonate, that has not yet been neutralized by reaction. On stirring the mass for some time, the alkaline reaction, however, will disappear and the product become quite neutral. The duration of time for complete conversion of the mixture depends on the quantity to be converted and upon the proportion of solvent used. The greater the quantity of mixture and the smaller the proportion of solvent used, the longer the time for conversion. The proportion of solvents may be varied within certain limits without altering the result.

The great advantages of this process over the known processes are, as stated,

small proportions of a single solvent are required for promoting reaction, that the output comes up to the theoretical yield and that decomposition of acetylsalicylic acid is preventedby the mild and protracted action of the alkali carbonate on theacid.

The following example illustrates the invention, but is in no way intended to limit it Example: 360 parts by Weight of finely above,

ground and sifted acetylsalicylic acid and 74 parts by weight of lithium carbonate are intimately mixed in a dry state and moistenedwith parts by weight of methylethylketone. The mixture is then kneaded well in a mixing machine, until a sample dissolves clearly in water without evolution of carbon dioxid. The lithium aeetylsalicylate, thus produced, is pressed in a dry filter cloth, broken to small pieces and dried first inthe open air, .then at a low temperature.

Lithium acetylsalicylate is a white powder, easily soluble in water with neutral reaction. When ferric chlorid is added to the aqueous solution, a flesh colored precipitate is formed. On adding dilute hydrochloric acid to the concentrated aqueous solution, free acetylsalicylic acid is precipitated which may be identified by its melting point. (134-135 centigrades).

Instead of methylethylketone any other of the organic liquids, mentioned above, may be used in a similar roportion for promotin reaction in the above example.

or the purpose of this invention alcohols of the aliphatic series are equivalents of ketones of the aliphatic series.

Having now described my invention, and in what manner the same is to be performed,

what I claim as new and desire to secure by Letters Patent is: I

Process of manufacturing lithium acetylsalicylate consisting in mixing equivalent quantities of acetylsalicylic acid and lithium carbonate intimately and in a dry state and ALBERT BUSCH.

Witnesses ALICE Boson, FRANZ AUSMEYER. 

